This invention relates to variable delivery vane compressors which have variable delivery quantities, and more particularly to a variable delivery vane compressor adapted for use in an air conditioning system for vehicles, which is adapted to have its delivery quantity of compressed refrigerant varied in response to operating conditions of a vehicle engine which drives the compressor.
A compressor used in an air conditioning system for automotive vehicles is generally driven by the engine of an automotive vehicle in which the air conditioning system is installed. The engine of the automotive vehicle, however, usually operates at various speeds from a low speed region such as idling to a high speed region. Since a compressor for air conditioning is required to exhibit satisfactory cooling performance even when the vehicle engine is operating in the low speed region, the capacity of the compressor, i.e. the delivery quantity of refrigerant per rotation is set to a somewhat large value so as to meet such requirement. This, however, results in an excessive cooling capacity of the air conditioning system as well as large power consumption of the engine during operation of the engine in the high speed region, that is, a large loss of energy. To avoid this disadvantage, an electromagnetic clutch has conventionally been employed for driving connection between the engine and the compressor. The clutch is disengaged to disconnect the compressor from the engine when a sensed discharge air temperature is below a predetermined value.
However, according to this conventional measure, at high air temperatures, the clutch is repeatedly engaged and disengaged with high frequency, which causes frequent changes in the load on the engine, giving a discomfortable feeling to the driver.
To overcome this drawback, a cooling system in an automotive vehicle has been proposed by U.S. Pat. No. 4,050,263 which employs a vane compressor adapted to reduce the refrigerant delivery quantity, i.e. perrotation volumetric throughput of the compressor in response to the rotational speed of the engine by arresting two diametrically opposite vanes in the retracted position when the engine is operating in a low or medium speed region.
However, according to this proposed compressor, the means for arresting the vanes in the retracted position has rather a complicated structure. Further, the arresting means is arranged within the rotor at a central portion thereof, requiring formation of a largesized internal space in the interior of the rotor for accommodating the arresting means, which imposes limitations upon the design of the compressor and also making it difficult to design the compressor compact in size.